Absolutely! There is a shuttle bus from the C concourse, and a walkable connection within the secure area from the B concourse (pretty cloudy here today, so the temperature in the all-glass walkway shouldn't be too bad; it's usually more overheated than the arrivals area at LHR). The shuttle bus leaves from somewhere in the area of C9 (I don't remember exactly where, but it's on the odd side on the low-numbered end), and the walkway is around B7.